I have two PCS. Both AMDs, but one newer then the other.
On my new one, AMD 8-core FX8120, 64-Bit, Asus board, the update run without any problem.
On my old one, AMD 4-core X4-965, 32-Bit, Gigabyte board, I had the same issue as all the others on this page.
Also on the X4-965 the compatibility check was ok, but still no success.
The difference between these machines is not big, both AMD based systems, the FX one just more uptodate. I could imagine that there is an issue with the Bios, becaue Win 8.1 expects some UEFI-Bios, and the older board might not be ready for that.
Or maybe because of the 32-bit, but I would expect that Microsofts would not install on 32-bit if not possible.
And I also selected a Swiss German keyboard after first power on in Win 8.1. But this keyboard selection was already in the filesafe system, it means directly after boot the PC crashed with blue screen (I saw the typically symbol :( that is used by Win 8 in
Bluescreen) and only after it went into the failsafe environment where I could go back to my old installation. Was actually not so easy to find the right option the bring the former Windows back.